Group III nitride nanorod light emitting device

ABSTRACT

There are disclosed a group III nitride nanorod light emitting device and a method of manufacturing thereof. The group III nitride nanorod light emitting device includes a substrate, an insulating film formed on the substrate, and including a plurality of openings exposing parts of the substrate and having different diameters, and first conductive group III nitride nanorods having different diameters, respectively formed in the plurality of openings, wherein each of the first conductive group III nitride nanorods has an active layer and a second conductive semiconductor layer sequentially formed on a surface thereof.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. application Ser. No.13/231,454, filed on Sep. 13, 2011, now U.S. Pat. No. 8,735,867 B2,which claims the priority of Korean Patent Application No.10-2010-0090117 filed on Sep. 14. 2010, in the Korean IntellectualProperty Office, the disclosures of which are incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a group III nitride nanorod lightemitting device, and more particularly, to a group III nitride nanorodlight emitting device and a method of manufacturing thereof.

2. Description of the Related Art

In general, a nanorod made of a group III-N alloy (for example, GaN) haspotential in the area of a new semiconductor device configuration, suchas a nano scale optoelectronic device. For example, a GaN nanorod mayprovide a device operating under corrosive or high temperatureconditions having chemical stability, a large bandgap, and a highmelting point advantageous to the device. In addition, the largerbandgap of GaN and related alloys may allow for the manufacturing of alight source within a visible range advantageous to applications indisplay and illumination devices. Moreover, the unique geometric shapesof individual nanorods may have the potential to provide a new paradigmin the field of photonics and transfer devices.

SUMMARY OF THE INVENTION

An aspect of the present invention provides a group III nitride nanorodlight emitting device capable of emitting light of various wavelengthsby growing group III nitride nanorods having different diameters on thesame substrate, and a method of manufacturing thereof.

According to an aspect of the present invention, there is provided agroup III nitride nanorod light emitting device, including: a substrate;an insulating film formed above the substrate, and including a pluralityof openings exposing parts of the substrate and having differentdiameters; and first conductive group III nitride nanorods havingdifferent diameters, respectively formed in the plurality of openings,wherein each of the first conductive group III nitride nanorods has anactive layer and a second conductive semiconductor layer sequentiallyformed on a surface thereof.

The insulating film may include a plurality of groups, each including aplurality of openings having the same diameter, and the plurality ofgroups have different diameters.

The active layer may include at least a pair of a quantum barrier layerand a quantum well layer.

The quantum barrier layer may be formed of Al_(y)Ga_(1-y)N(0≦y≦1), andthe quantum well layer may be formed of In_(x)Ga_(1-x)N(0≦x≦1).

The active layer formed on each of the first conductive group IIInitride nanorods may have a content of indium (In) less than that ofanother active layer formed on another first conductive group IIInitride nanorod having a smaller diameter.

The light emitting device including the first conductive group IIInitride nanorods having different diameters may emit light of differentwavelengths.

According to another aspect of the present invention, there is provideda method of manufacturing a group III nitride nanorod light emittingdevice, the method including: forming an insulating film including aplurality of openings exposing parts of a substrate and having differentdiameters on the substrate; growing first conductive group III nitridenanorods having different diameters in the openings; and sequentiallyforming an active layer and a second conductive semiconductor layer on asurface of each of the first conductive group III nitride nanorods.

The first conductive group III nitride nanorods may have diametersformed to be greater than those of the openings by 10% to 20%.

The active layer may include a quantum barrier layer formed ofAlyGa1-yN(0≦y≦1) and a quantum well layer formed of GaN.

The active layer formed on each of the first conductive group IIInitride nanorods may have a content of indium (In) less than that ofanother active layer formed on another first conductive group IIInitride nanorod having a smaller diameter.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and other advantages of thepresent invention will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a cross sectional view of a group III nitride nanorod lightemitting device including a plurality of group III nitride nanorodshaving different diameters according to an exemplary embodiment of thepresent invention;

FIGS. 2A through 2C are diagrams showing a forming process of aninsulating film including a plurality of openings having differentdiameters on a substrate according to an embodiment of the presentinvention;

FIG. 3 is a plan view of the insulating film including the plurality ofopenings having different diameters formed therein; and

FIGS. 4A through 4C show a process of manufacturing a group III nitridenanorod light emitting device in which nanorods are provided in aninsulating film including a plurality of openings having differentdiameters, according to an exemplary embodiment of the presentinvention;

FIGS. 5A through 5C are scanning electron microscope (SEM) micrographsof first conductive group III nitride nanorods, the growths of whichhave been completed, according to an exemplary embodiment of the presentinvention; and

FIG. 6 is a graph showing PL properties of a group III nitride nanorodlight emitting device including light emitting structures havingdifferent diameters, according to an exemplary embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Exemplary embodiments of the present invention will now be described indetail with reference to the accompanying drawings. The invention may,however, be embodied in many different forms and should not be construedas being limited to the embodiments set forth herein. Rather, theseembodiments are provided so that this disclosure will be thorough andcomplete, and will fully convey the scope of the invention to thoseskilled in the art. While those skilled in the art could readily devisemany other varied embodiments that incorporate the teachings of thepresent invention through the addition, modification or deletion ofelements, such embodiments may fall within the scope of the presentinvention.

The same or equivalent elements are referred to by the same referencenumerals throughout the specification.

FIG. 1 is a cross sectional view of a group III nitride nanorod lightemitting device including a plurality of group III nitride nanorodshaving different diameters according to an exemplary embodiment of thepresent invention. Referring to FIG. 1, the group III nitride nanorodlight emitting device may include a substrate, a buffer layer, aninsulating film, and a plurality of light emitting structures,respectively including group III nitride nanorods.

A substrate 100 is a growth substrate for growing a semiconductor singlecrystal, in particular, a nitride single crystal. The substrate 100 maybe, for example, made of a material, such as a sapphire, silicon (Si),zinc oxide (ZnO), gallium arsenide (GaAs), silicon carbide (SiC),MgAl₂O₄, magnesium oxide (MgO), lithium aluminate (LiAlO₂), LiGaO₂,gallium nitride (GaN), or the like. The sapphire is a crystal havingHexa-Rhombo R3c symmetry, and has a C(0001)-plane, an A(1120)-plane, anR(1102)-plane, or the like. In this case, since the C-plane may berelatively facilitated for the growth of a nitride thin film, and stableat a high temperature, the C-plane may be mainly used for a substratefor growing a nitride semiconductor.

A buffer layer 110 is a nitride semiconductor layer, and may be made ofa semiconductor material formed of Al_(x)In_(y)Ga_((1-x-y))N (0≦x≦1,0≦y≦1, 0≦x+y≦1) doped with impurities. For example, gallium nitride(GaN), aluminium gallium nitride (AlGaN), indium gallium nitride(InGaN), or the like may be used as the buffer layer 110. The bufferlayer 110 may be formed of an n-type nitride semiconductor layer or ap-type nitride semiconductor layer according to the requirementsthereof. Silicon (Si), germanium (Ge), selenium (Se), tellurium (Te) orthe like may be used as n-type impurities, and magnesium (Mg), zinc(Zn), beryllium (Be) or the like may be used as p-type impurities.

The insulating film 120 may function to prevent contact between then-type nitride semiconductor layer and the p-type nitride semiconductorlayer of the nanorod light emitting device. In consideration of thisfunction, the insulating film 120 may be made of a silicon oxide or asilicon nitride, for example, a silicon dioxide (SiO₂), a titaniumdioxide (TiO₂), a silicon nitride (Si₃N₄) or the like. The height of theinsulating film may be, for example, approximately 50 to 100 nm. Theinsulating film 120 may include a plurality of openings (not shown)exposing parts of the buffer layer 110. The plurality of openings havedifferent diameters and may be patterned on the insulating film 120. Theopenings are means to designate a diameter, a length, a position ofnanorods to be grown by a batch process. The openings may have variousshapes, such as a quadrangle, a hexagon or the like, as well as beingcircular.

A plurality of light emitting structures 165, 175, and 185, respectivelyincluding first conductive group III nitride nanorods having differentdiameters are formed in the openings. The light emitting structures 165,175, and 185 may include first conductive group III nitride nanorods160, 170, and 180, active layers 161, 171, and 181, and secondconductive semiconductor layers 162, 172, and 182.

The first conductive group III nitride nanorods 160, 170, and 180 may beformed of a single crystal, and may be made of n-GaN or p-GaN. Thediameters of the first conductive group III nitride nanorods 160, 170,and 180 may be substantially proportional to diameters of the openings,and may be formed to be greater than those of the openings in which thefirst conductive group III nitride nanorods 160, 170, and 180 areformed, by approximately 10% to 20%. The length of the first conductivegroup III nitride nanorods 160, 170, and 180 may be adjusted bycontrolling time spent at a batch process temperature.

The active layers 161, 171, and 181 may be grown as a single crystal, inthe same manner as the first conductive group III nitride nanorods 160,170, and 180. The active layers 161, 171, and 181 may be grown to emitlight having a predetermined energy by the light-emitting recombinationof electrons and electron holes. The active layers 161, 171, and 181 mayinclude at least a pair of a quantum barrier layer and a quantum welllayer. The active layers 161, 171, and 181 may have a multiple quantumwell structure. Byway of example, the quantum barrier layer may beformed of Al_(y)Ga_(1-y)N(0≦y≦1), and the quantum well layer may beformed of In_(x)Ga_(1-x)N(0≦x≦1), whereby bandgap energy or lightemitting wavelength may be adjusted depending on the content of indium(In).

The thickness of the second conductive semiconductor layers 162, 172,and 182 may be approximately 20 nm or more. When the first conductivegroup III nitride nanorods 160, 170, and 180 are n-type semiconductors,the second conductive semiconductor layers 162, 172, and 182 may bep-type semiconductor layers. While, when the first conductive group IIInitride nanorods 160, 170, and 180 are p-type semiconductors, the secondconductive semiconductor layers 162, 172, and 182 may be n-typesemiconductor layers.

FIGS. 2A through 2C are diagrams showing a process of forming aninsulating film including a plurality of openings having differentdiameters on a substrate according to an embodiment of the presentinvention.

Referring to FIG. 2A, the buffer layer 110 maybe formed on the substrate100. The buffer layer 110 may be grown by a process, such as a metalorganic chemical vapor deposition (MOCVD), a molecular beam epitaxy(MBE), a hydride vapor phase Epitaxy (HVPE) or the like. By way ofexample, a C(0001)-plane sapphire substrate is prepared in a reactorwithin a MOCVD apparatus to apply heat thereto, thereby allowing for thedeposition of the buffer layer 110, a n-GaN semiconductor layer on thesubstrate at a temperature of about 1080° C.

Referring to FIGS. 2B through 2C, the insulating film 120 may be formedon the buffer layer 110. A plurality of patterned openings 130, 140, and150 exposing parts of the buffer layer 110 may be formed in theinsulating film 120. The patterned openings 130, 140, and 150 may beformed in the insulating film 120 by etching the insulating film 120through a lithography process. By way of example, the openings 130, 140,and 150 having different diameters may be formed in the insulating film120 in such a manner as to have certain diameters W1, W2 and W3 anddistances therebetween. The respective diameters W1, W2 and W3 of theopenings 130, 140, and 150 shown in FIG. 1C are in accordance with theorder in size of W1<W2<W3.

FIG. 3 is a plan view of the insulating film including the plurality ofopenings having different diameters formed therein. Referring to FIG. 3,the insulating film 120 may include a plurality of groups, eachincluding a plurality of openings having the same diameter, and theplurality of groups may have different diameters. The openings 130, 140,and 150 are means to designate a diameter, a length, and a position ofthe nanorods to be grown by a batch process. The openings 130, 140, and150 may have various shapes, such as a quadrangle, a hexagon or thelike, as well as being circular.

FIGS. 4A through 4C show a process of manufacturing a group III nitridenanorod light emitting device in which nanorods are provided in aninsulating film including a plurality of openings having differentdiameters, according to an exemplary embodiment of the presentinvention.

Referring to FIG. 4A, the respective first conductive group III nitridenanorods may be grown to a height of the insulating film 120 on thebuffer layer 110 exposed by the plurality of openings of the insulatingfilm 120. In the process, byway of example, while a temperature in thereactor equipped with the substrate 100 may be maintained atapproximately 900° C. to 1100° C. and a gallium source, trimethylgallium (TMGa) of about 10 sccm to 200 sccm and an ammonia (NH₃) gas of15000 sccm to 20000 sccm are scattered, the respective first conductivegroup III nitride nanorods may be deposited to the height of theinsulating film 120, that is, approximately 50 to 100 nm at atemperature of approximately 1000° C. to 1100° C. for about 1 min to 5min.

After the first conductive group III nitride nanorods are grown to theheight of the insulating film 120, the flow rate of the gallium source,TMGa, may be reduced to approximately 50 to 150 sccm and the flow rateof ammonia (NH3) gas may be reduced to approximately 500 to 5000 sccm,and the first conductive group III nitride nanorods 160, 170, and 180may be grown at approximately 900 to 1100. At this time, the internalpressure of the reactor may be maintained to approximately 70 mbar to200 mbar.

The respective diameters of the first conductive group III nitridenanorods 160, 170, and 180, the growths of which have been completed onthe substrate 100, are in accordance with the order of W4<W5<W6.However, the respective heights of the first conductive group IIInitride nanorods 160, 170, and 180 are in accordance with the order ofH1>H2>H3. Therefore, the diameters and the heights thereof may be ininverse proportion.

FIGS. 5A through 5C are scanning electron microscope (SEM) micrographsof first conductive group III nitride nanorods, the growths of whichhave been completed, according to an exemplary embodiment of the presentinvention. Referring to FIGS. 5A through 5C, while the diameters of thefirst conductive group III nitride nanorods are in accordance with theorder in size of FIG. 5A<FIG. 5B<FIG. 5C, the heights of the firstconductive group III nitride nanorods are in accordance with the orderof FIG. 5A>FIG. 5B>FIG. 5C. The lengths of the first conductive groupIII nitride nanorods may be adjusted by controlling time spent at thebatch process temperature.

According to the exemplary embodiment of the present invention, when thepatterned openings of the insulating film have diameters in the range ofapproximately 100 to 180 nm, the grown first conductive group IIInitride nanorods have diameters in the range of approximately 120 to 200nm. When the patterned openings of the insulating film have diameters inthe range of approximately 180 to 250 nm, the grown first conductivegroup III nitride nanorods have diameters in the range of approximately200 to 280 nm. When the patterned openings of the insulating film havediameters in the range of approximately 250 to 400 nm, the grown firstconductive group III nitride nanorods have diameters in the range ofapproximately 280 to 450 nm. Therefore, it can be confirmed that thediameters of the first conductive group III nitride nanorods may besubstantially proportional to the diameters of the patterned openings,and the diameters of the nanorods may be formed to be larger than thoseof the patterned openings by approximately 10% to 20%.

Referring to FIG. 4B, the active layers 161, 171, and 181 are formed onthe surfaces of the first conductive group III nitride nanorods 160,170, and 180 formed above the substrate 100 on which the buffer layer110 and the insulating film 120 are sequentially stacked. In anexemplary embodiment, the formation of the active layers 161, 171, and181 may be performed at a temperature lower than the formationtemperature of the first conductive group III nitride nanorods 160, 170,and 180 by approximately 100° C. to 300° C.

Referring to FIG. 4C, the second conductive semiconductor layers 162,172, and 182 may be formed on the active layers 161, 171, and 181 so asto cover the entire surfaces of the active layers 161, 171, and 181.

FIG. 6 is a graph showing PL properties of a group III nitride nanorodlight emitting device including light emitting structures havingdifferent diameters, according to an exemplary embodiment of the presentinvention. After n-GaN nanorods having different diameters were formed,active layers having five pairs of InGaN/GaN were formed thereon, andthen p-GaN layers were formed thereon, whereby nanorod light emittingstructures were formed. The PL properties of the nanorod light emittingstructures having different diameters and grown under the same growthcondition are shown in FIG. 6. Referring to FIG. 6, in the case of ananorod light emitting structure 51 having a larger diameter, it showsan emission wavelength shorter than that of a nanorod light emittingstructure 52 having a smaller diameter. Thus, it can be confirmed thatthe content of In contained in the active layer of the nanorod lightemitting structure having a larger diameter is less than that of thenanorod light emitting structure having a smaller diameter. As a result,it can be seen that the content of In contained in the nanorod lightemitting structures grown under the same conditions may be increased, asthe diameter of nanorods is reduced. It can be confirmed that thevariation range of the PL wavelength may be changed in the range of 420to 480 nm, as the diameter of the patterns is changed within the rangeof 200 to 400 nm.

As set forth above, according to exemplary embodiments of the invention,there are provided a group III nitride nanorod light emitting devicecapable of emitting light of various wavelengths by growing group IIInitride nanorods having different diameters on the same substrate, and amethod of manufacturing thereof.

While the present invention has been shown and described in connectionwith the exemplary embodiments, it will be apparent to those skilled inthe art that modifications and variations can be made without departingfrom the spirit and scope of the invention as defined by the appendedclaims.

What is claimed is:
 1. A method of manufacturing a group III nitridenanorod light emitting device, the method comprising: forming a firstconductive semiconductor layer on a substrate forming an insulating filmincluding openings exposing parts of the first conductive semiconductorlayer; growing first conductive group III nitride nanorods, respectivediameters of the first conductive group III nitride nanorods being 120nm or greater; and forming light emitting structures by sequentiallyforming an active layer and a second conductive semiconductor layer on asurface of each of the first conductive group III nitride nanorods suchthat the active layer is positioned on a side surface of the firstconductive group III nitride nanorod, wherein the light emittingstructures are divided into at least two groups including a first groupon a first area of the first conductive semiconductor layer and a secondgroup on a second area of the first conductive semiconductor layer, eachgroup including two or more light emitting structures that havesubstantially identical diameters and substantially identical heights,wherein the diameter of the light emitting structures of the first groupis smaller than the diameter of the light emitting structures of thesecond group and an active layer of the second group emits second lighthaving a different wavelength from that of the first light emitted by anactive layer of the first group, and wherein the active layer of thesecond group has an indium (In) content smaller than that of the activelayer of the first group.
 2. The method of claim 1, wherein thesubstrate comprises a material selected from the group consisting of asapphire, silicon (Si), zinc oxide (ZnO), gallium arsenide (GaAs),silicon carbide (SiC), MgAl₂O₄, magnesium oxide (MgO), lithium aluminate(LiA1O₂), LiGaO₂ and gallium nitride (GaN).
 3. The method of claim 1,wherein the substrate is a sapphire substrate having a C(0001)-plane, anA(1120)-plane, or an R(1102)-plane.